Neumann Vintage U87 Clone : Build Thread.

[sr1200]

Just listened again, the only noise im hearing is the noise from your room which i cant really separate from any apparent hiss in the mic itself.  There are no real dead air breaks in there where you can hear self-noise.  Put the mic in a noiseless closed room and record some dead air.  Would be way easier to tell.

 

[kante1603]

Just listened again, the only noise im hearing is the noise from your room which i cant really separate from any apparent hiss in the mic itself.  There are no real dead air breaks in there where you can hear self-noise.  Put the mic in a noiseless closed room and record some dead air.  Would be way easier to tell.

I absolutely agree with sr1200,the mic seems to be o.k.
I don't trust your signal chain when you say you use the onyx as a converter.With the mp73 in use,which input of the onyx is used?
Also you're talking about compressor use,sometimes two.Any compression will bring up the noise floor,whether surrounding noise,the electrical generated system noise or both.
Personally I've never made good experiences in using an onyx via firewire.A nice little mixer in my opinion,not more.
Maybe you could try a different interface too......just a thought.....

Udo.

 

[burglar]

Hiya,

Thanks for your replies.  It's the spoken word recordings that worry me.  especially the 8" from grill.  The noise is best heard right at the end of the 8" from grill clip where the dead air break is longest.  You can see it on the wave form.  It's not the ambient noise that worries me.  It's the low level white noise / hiss.  there is slight compression, but it's just catching the peaks.  Not enough to bring up the noise significantly. 

If you listen to the 8" clip, it is audible whilst speaking.  Certainly couldn't do voice over work with it.  I would like to say it is the Onyx so I'd have an excuse to pocket out on some new converters but I don't have this with any of my other mics.  I compared with an MXL 2010 and the noise floor is virtually non existent.  The onyx is a pretty flat sounding box.  Nothing exciting but it's pretty quiet.   

 

[kante1603]

We mustn't talk about this "console",I know it.
As said it is about seeing the complete signal chain.not just single parts of it.
As said any compression does(!) increase the noise floor.
You didn't answer my question concerning how the mp73 is connected.
Remember a vintage U87 does have less output level,so you have to bring it up somewhere.
Most of times white noise indicates a classic system noise.
If your other mics are doing it better-why not use them?

 

[burglar]

Thanks for your reply Udo,

The MP73 is going at line level into a channel on the desk whereupon it goes through the conversion stage and into cubase.

My post was purely about the self noise of the mic.  I definitely prefer the sound of the 87 over my other condensers and I certainly would not say they do it better.  They are just quieter. 

I have a/b'd  with/without the light compression and there is no significant change in the level of the noise.  If you think it would help I can re post the clips?



 

 

[kante1603]

Thanks for your reply Udo,

The MP73 is going at line level into a channel on the desk whereupon it goes through the conversion stage and into cubase.

That is correct,gain at unity?

My post was purely about the self noise of the mic.  I definitely prefer the sound of the 87 over my other condensers and I certainly would not say they do it better. 

You can´t talk about self noise until you have isolated it.

They are just quieter. 

....or have a higher output which means less gain is needed.More gain means more (white) noise.

I have a/b'd  with/without the light compression and there is no significant change in the level of the noise. 

I didn´t say "significant",but it does after make-up.

If you think it would help I can re post the clips?

No,not needed.

If you want to seperate this to hear or see the system noise you can do as follows:
Set up your U87 as usual with the same gain you did before.Unplug it and do not alter anything (monitor speakers off of course!).
Now instead of the mic you can strap a-say- 200Ohms resistor over the input of your preamp,just take an xlr plug and solder the resistor to pin 2 & 3,pin 1 not connected).You now simulate the load of a typical mic to your signal chain.Record it as usual.
When you now zoom into the waveform you can see the generated system noise,bring up the volume and you can hear it.

Measuring the self-noise of the mic is a bit more difficult,at least you can measure the mic´s electronics with a 50pf cap instead of the capsule attached.
Everything else is too complicated and could be very expensive (mic in an unechoic chamber or a "Rauschbombe",exclusive measuring instruments etc.).

The U87 is definetely not the quietest mic in the world but should still have good specs,the original e.g. has 69 dB refering 1Pa.

Have built four of them and I´m happy with them and my pro environments,

Udo.

 

[poctop]

What is your final drain voltage Value for the bias ?,  Might somthing not set proper in the bias as this will affect the gain tremendoulsy if not setup right ,

I havent heard the sample yet but i will soon , i am just ouf of town and out of listening gear for now

And Again i wish to thank all of you guys that are helping folks get sucessfull in this build 



Best,
Dan,

 

[sr1200]

Udo, I have to agree on everything you said with this issue.  The mic's output level alone is going to make the mic seem a lot "noiser" than say the MXL just because of that level difference and the gain needed to push the mics to the same level.  Using a mackie onyx as the pre is really not the tool to check this.  That mic is going to need somewhere in the higher end of the mackies gain to get that mic up to par and at that point you're hearing the noise of the mackie over whatever is plugged in...  Acutally you dont even need to plug anything into the pre on the mackie, just pump the gain and listen to the output, you'll hear the noise.

 

[0dbfs]

Udo, I have to agree on everything you said with this issue.  The mic's output level alone is going to make the mic seem a lot "noiser" than say the MXL just because of that level difference and the gain needed to push the mics to the same level.  Using a mackie onyx as the pre is really not the tool to check this.  That mic is going to need somewhere in the higher end of the mackies gain to get that mic up to par and at that point you're hearing the noise of the mackie over whatever is plugged in...  Acutally you dont even need to plug anything into the pre on the mackie, just pump the gain and listen to the output, you'll hear the noise.

Yeah but it's an un-terminated input at that point. At least put a 150-200r resistor across the pins 2/3 if you want to hear the pre more accurately without mic. Try that with any pre you have and crank the gain and mon's. Interesting and revealing.

Cheers,
j

 

[kante1603]

Absolutely needed-and easy to do,takes just a minute....

Thanks j,

Udo.

 

[kante1603]

And now my 1000th post:

We're off-topic ;D ;D ;D.........

Best,

Udo.

 

[poctop]

And now my 1000th post:

We're off-topic ;D ;D ;D.........

Best,

Udo.

Congrats,  ;D
Best,
Dan,

 

[burglar]

Thanks for your posts guys,

Will read through them again in the morning and put them into practice.  Regarding my FET voltage, it is 11.3.  I know it is best to scope bias but the signal generator I got doesn't have enough output to get the job done.  Aiming to get it done asap. 

 

[kante1603]

I know it is best to scope bias but the signal generator I got doesn't have enough output to get the job done.

So you have a daw which might contain a signal generator,If not you can download one or get a -say- 1k sine wave as a wav or aif-file from the web,no problem.
Any normal interface will output +14 or +18dBu at zero dBFS at a reference voltage of 0,775v.
That means an output signal of 3,882 or 6,153v.Most of interfaces refer to a zero dB level of +4dBu which is a studio standard,so the output can be as much as 9,752v.So nearly 10 volts is not enough to get the circuit clipping?
Interesting.....and I don't believe in it,sorry.

Udo.

 

[burglar]

Hi Udo,

I didn't try using my DAW.  I borrowed a small generator off a friend and it didn't have the guts.  Will attempt with comp.

 

[taffer]

Hi !
I made this clone U87 ... I'm happy! The sound is good, detailed at the top of the spectrum and dynamic!
All this at a lower cost and the pleasure of doing it yourself !

Thank you to Poctop, Chunger, Matador and all those who participated in this project!

PS: Sorry for my English ... I'm french and I do not speak very well ...

 

[taffer]

And now, I'll start the C12 clone !

After the feet, the tube !

 

[kante1603]

Hi !
I made this clone U87 ... I'm happy! The sound is good, detailed at the top of the spectrum and dynamic!
All this at a lower cost and the pleasure of doing it yourself !

Thank you to Poctop, Chunger, Matador and all those who participated in this project!

PS: Sorry for my English ... I'm french and I do not speak very well ...

Congrats and welcome to the forum!

 

[jasonallenh]

Hey guys, just posting this question because it slipped through the cracks :'(

I have the three toggle switches from my bhrngr B-2, and I was wondering how to correctly connect them to the PCB (i'm bypassing the switch PCB, so i intend to have it wired correctly to match the polar pattern label) if I were to connect them directly. It appears the polar pattern switch is center off, and the other two are spst. I can't quite make out what leads must be  connected with jumpers do make certain options activate, so if someone could help explain how the switching works, I can move on in my build!

Thanksssssssssss

 

[wink0195]

Please help!

I am experiencing the same ami t13 transformer reversal that Chuger at studio939 experienced during his build.

Quote from Chunger's Blog:
"Because a large number of T13's were shipped with wire markings reversed from the spec sheet, I checked my transformer and it read about 21R on the yellow side and about 436R on the black side, so mine was reversed.  The higher resistance side (yellow in my case) should go towards the capsule side and the lower resistance side (black in my case) should go to the output xlr.
I didn't want to mess up my polarities so I tried following the diagram and reversing the colors since I don't have the foggiest idea what the silk-screened letter indications on the transformer pads mean."

I however do know what the indication on the transformer pads mean:
ws - secondary high (+)
bl - secondary low (-)
sw - primary low (-)
rot - primary high (+)

I'd probably follow chunger's build, if my transformer wasn't so different. The leads on my T13 are coming out of the bottom (in relation to the AMI t13 yellow tape label) whereas Chungers T13's leads come out of the top -- so I suspect right and left comparing our transformers may very well be flipped. 

How can I test the polarity of my AMI T13 which has reversed colors and how should i wire it to the pads? Can I use a simple 9v battery to test step down vs step up nature of a transformer?

Thanks for listening - Andrew